1. Field of the Invention
The present invention relates to an automotive alternator and particularly to a stator construction enabling heat dissipation of heat generated in stator winding joint portions to be improved and deterioration in application workability and quality of an electrically-insulating resin to be suppressed.
2. Description of the Related Art
In a first conventional stator for an automotive alternator, a plurality of continuous conductor wires are each wound for one round into a wave winding in slots separated by a predetermined number of slots so as to alternately occupy an inner layer and an outer layer in a slot depth direction, winding phase portions being constructed by joining together end portions of the continuous conductor wires installed in identical slot groups. Portions of each of the continuous conductor wires exiting the slots and entering slots a predetermined number of slots away, in other words coil ends, are arranged so as to be aligned in rows in a circumferential direction so as to line up two rows deep in a radial direction, constituting coil end groups. In addition, annular shielding plates each having an L-shaped cross section are disposed so as to cover an inner circumferential side and an apex portion of each of the coil end groups, and an epoxy resin is applied to the coil end groups so as to embed the shielding plates. At this time, the epoxy resin is interposed between the shielding plates and the coil ends so as to have a predetermined thickness. (See Patent Literature 1, for example.)
Here, in joint portions, an electrically-insulating coating covering the end portions of the continuous conductor wires is removed, leaving the metal base material of the conductor wires in an exposed state. Thus, in order to suppress short-circuiting between the joint portions, galvanic corrosion of the joint portions, etc., it is necessary to electrically insulate the joint portions. However, in this first conventional stator for an automotive alternator, no mention is made of electrically-insulating treatments for the joint portions. Thus, in the first conventional stator for an automotive alternator, the shielding plates are disposed so as to cover the apex portions of the coil end groups, including the joint portions, and if the epoxy resin is applied to the coil end groups and the joint portions, the resin is interposed so as to have a predetermined thickness not only between the shielding plates and the coil ends, but also between the shielding plates and the joint portions. Electrical resistance is greater in these joint portions than in other portions of the continuous conductor wires, increasing the amount of heat generated. As a result, the heat generated cannot dissipate effectively, not only in the coil ends, but also in the joint portions where the amount of heat generated is the greatest. In addition, the epoxy resin also serves to secure the shielding plates and the coil ends (including the joint portions) but there is no means for positioning the shielding plates and the shielding plates move easily as the epoxy resin is being applied, leading to deterioration in the application and quality of the electrically-insulating resin.
In a second conventional stator for an automotive alternator, a stator winding is constructed by inserting U-shaped conductor segments into pairs of slots in a stator core from a first end and joining together free ends of the conductor segments projecting outward at a second end of the stator core. Joint portions are arranged so as to form two rows in a circumferential direction and to line up in single columns in a radial direction, constituting a coil end group. In addition, a cap having a double-row construction which has an annular shape and is provided with two chambers is placed over the coil end group such that each row of the joint portions arranged so as to form two rows in a circumferential direction is housed in each of the chambers, each of the chambers being filled with an electrically-insulating resin to electrically insulate the joint portions. (See Patent Literature 2, for example.)
However, in the second conventional stator for an automotive alternator, because the widths of the chambers of the cap are formed so as to be wider than the radial lengths of the joint portions, the injected electrically-insulating resin is thick and excessive around outer edge portions of each of the joint portions, preventing the heat generated in the joint portions from dissipating efficiently. The electrically-insulating resin also serves to secure the cap and the joint portions, but the cap is not positioned in a reliably secured state and moves easily, particularly in a radial direction radially outside or radially inside the range of the coil ends, making both workability and quality poor. Contact between the cap and internal components of the alternator is also of concern.
Patent Literature 1: Japanese Patent Laid-Open No. 2001-245454 (Gazette: FIG. 14)
Patent Literature 2: Japanese Patent Laid-Open No. 2000-209802 (Gazette: FIG. 5)
In these conventional stators for an automotive alternator, because the electrically-insulating resin is interposed thickly between the shielding plates (or the cap) and the joint portions, one problem has been that the heat generated in the joint portions is prevented from dissipating efficiently, causing the temperature of the stator winding to rise excessively and preventing high output from being achieved. Another problem has been that positioning of the shielding plates (or the cap) is insufficient, reducing workability and quality. Thus, there has been a risk that contact may occur with the internal components of the alternator if the shielding plates or the cap is misaligned.